The present invention pertains to a rubber bearing with graduated damping characteristic, which comprises, in the known manner, essentially a preferably cylindrical or approximately cylindrical inner part, a tubular outer sleeve arranged coaxially around the inner part, as well as a pressure body with chambers for a damping agent, which is arranged in a fixed manner between the inner part and the outer sleeve.
Corresponding to the versatility of their use, rubber bearings must have greatly different properties in terms of their damping characteristic, and they are also stressed by the forces absorbed by them to different extents. Their damping characteristic is therefore optimized for the particular application by a suitable design of their geometry and/or by the selection of the elastomer of which the pressure body consists. Nevertheless, it is desirable to achieve a certain flexibility in manufacture in providing bearings with different properties. The bearings are also frequently subject to dynamically greatly varying conditions in terms of the forces acting on them during their practical use. It is therefore known that the bearings can be designed such that they can be adapted to the intended use during manufacture in a simple manner or that they have a certain broad range of dynamic damping characteristics.
A design of a rubber bearing which is said to make it possible to adapt its elastic properties to different needs during the manufacture in a simple manner has already become known through DE 39 09 609 A1. This document describes a rubber bearing in which a second spring body, which is arranged at a radially spaced location from the first spring body in the gap between the inner part and the outer sleeve, is arranged in parallel to the first pressure or spring body. The second spring body is designed as a two-part body in the form of an elastomer element provided on both front sides of the bearing. Damping of the bearing, which is supported by a liquid damping agent, is not provided according to the solution according to this document. The bearing is also suitable only conditionally for use for damping vibrations with amplitudes or frequencies in different ranges of the characteristic.
A hydraulically damping rubber bearing, which brings about vibration damping in two different frequency ranges, has been known from DE 42 22 486 A1. A plurality of chambers filled with a damping liquid are formed for this purpose in the spring element or pressure body. According to this solution, two outer chambers connected to one another via a channel in a liquid-carrying manner surround a chamber located radially farther inward. The chambers are limited against one another by rubber elastic expandable walls in their axial succession. According to the document, good insulation of higher-frequency vibrations is achieved by the inner chamber. The outer area of the spring element consequently has mainly a vibration-damping effect, whereas the inner area has a vibration-insulating effect. The comparatively great manufacturing effort for such a bearing can be considered to be disadvantageous. This is true especially concerning the liquid-tight mounting of the two vulcanized parts.
The object of the present invention is to provide a rubber bearing which has a simple design and effectively damps forces introduced in different ranges of the characteristic due to its graduated damping characteristic, while avoiding the drawbacks of the state of the art.
According to the invention, the bearing includes an inner part of a cylindrical or approximately cylindrical shape, a tubular outer sleeve arranged coaxially around the inner part, as well as a pressure body with chambers for accommodating a liquid damping agent. The pressure body is arranged between the above-mentioned parts. The pressure body is divided in the radial direction into a plurality of damping areas which can be adjusted in terms of their damping characteristics independently from one another by at least one intermediate sleeve arranged coaxially to the inner part and the outer sleeve.
A design that is certainly needed most often in practice and is obvious in terms of a compromise between the best possible damping and the manufacturing effort needed therefor concerns an embodiment with two damping areas in relation to the radial direction. According to the invention chambers for a damping agent may be provided within both damping areas of the pressure body in an embodiment. To achieve the completely closed nature of the damping areas, i.e., damping characteristics that do not mutually affect each other, there is a liquid-carrying connection only between the chambers of one damping area. An exchange of damping agent is not possible between the different damping areas due to the inserted intermediate sleeve.
Corresponding to a possible embodiment, which can be advantageously used, e.g., for mounting the suspension arms of a vehicle, the inner damping area has a softer characteristic than the outer damping area. However, an opposite design is also conceivable for special purposes to reduce the stress on the bearing. Besides the selection of different elastomers to form the damping areas, the different damping characteristics of these damping areas can also be achieved by the use of different types of damping agents of different viscosities for filling the chambers of the damping areas.
In a special embodiment of the rubber bearing, which is also intended for special applications, at least one damping area or both damping areas has different damping characteristics with respect to forces introduced from different radial directions. Depending on the generally desired damping characteristic, this can be achieved by a corresponding shaping of the inner part or of the elastic pressure body.
According to another embodiment of the bearing according to the present invention, the damping areas have different axial lengths due to a corresponding dimensioning of the elastomer as well as of the intermediate or separating sleeve or sleeves. In a bearing with two damping stages, the outer damping stage preferably has a shorter axial extension than the inner one.
The bearing according to the present invention makes possible an effective gradation of the damping characteristics despite its comparatively simple design and the resulting simple mounting. In the case of a characteristic that is softer toward the middle, shock and vibration loads of high frequency and low amplitude are first damped effectively by the inner damping area of the bearing. If the forces that occur become stronger, i.e., if their amplitude increases, the inner area will come to a stop. Without the presence of a second damping stage, the damping would now be brought about exclusively by the elastomer. On the one hand, there would not be such an effective damping any more as a result, and, on the other hand, the pressure body would be stressed enormously. However, the outer damping area adjusted with the harder range of the characteristic is activated when the inner damping comes to the stop due to the embodiment according to the present invention. Due to the complete uncoupling of the two damping areas, these can have very great differences in terms of their stiffness and each can be adjusted to preset frequencies separately.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated.